<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <!--<script src="https://cdn.bootcss.com/jquery/3.4.1/core.js"></script>-->
    <script src="lib/jquery-3.4.1.js"></script>
</head>
<body>

<a href="" id="test-jquery">点我</a>

<script>

    //选择器就是css的选则器
    $('#test-jquery').click(function () {
        alert('hello,jQuery');
    })

</script>

</body>
</html>